Flask



FIG. 1 is a front, left perspective view of the flask showing my new design;

FIG. 2 is a front view thereof, the rear view being a mirror image thereof;

FIG. 3 is a left side view thereof, the right side view being a mirror image thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof.

The broken lines shown in the drawings are included for the purpose of illustrating environmental structure and form no part of the claimed design. 

CLAIM The ornamental design for a flask, as shown and described. 